Ultrasonic cleaning method and apparatus therefore

ABSTRACT

Ultrasonic cleaning apparatuses and methods of cleaning substantially planar articles. An apparatus comprises (i) a substantially circular tank; (ii) a plurality of cleaning fluid inlets for delivering a cleaning fluid to the tank; (iii) an intermediate support for receiving an article to be cleaned; and (iv) an ultrasonic generator coupled to the tank for generating ultrasonic waves in the tank and cleaning fluid received therein. The apparatus is configured to remove particles from a substantially planar article and have them carried by flow of cleaning fluid away from the article and out of the tank. Using such an apparatus, a cleaning method comprises introducing a substantially planar article to be cleaned into the tank; introducing a cleaning fluid into the tank through the plurality of cleaning fluid inlets; and exciting the cleaning fluid with ultrasonic waves.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority under 35 USC§120 to co-pending U.S. patent application Ser. No. 13/711,962 filed onDec. 12, 2012, entitled “Ultrasonic Cleaning Method and ApparatusTherefore” which is hereby incorporated by reference for all purposes.

FIELD

This disclosure relates to methods of ultrasonically cleaning articlesand apparatuses therefore, and more particularly to methods andapparatuses for cleaning quartz windows of plasma processing chambers.

BACKGROUND

In industrial processes, component surfaces are typically exposed toenvironments that erode or contribute to build-up on such surfaces.Thus, new components must be cleaned before first use, and over time,surfaces of such components must be cleaned in order for them tocontinue to be useful. Otherwise, such surfaces (or whole components)must be replaced. Due to cost concerns, cleaning a surface is oftenpreferable to replacement. However, certain surfaces are difficult toclean due to the nature of the component and the environment to which itis exposed. For example, semiconductor substrate materials (such assilicon wafers) are processed in plasma processing chambers whereininterior and interior-facing surfaces are exposed to deposition,etching, and stripping environments. Thus, accumulation of inorganic andorganic contaminates on component surfaces is commonly observed and cancause product contamination, reduction in processing efficiency, orboth.

One example of a surface in a plasma processing chamber is a quartz(SiO₂) surface. Chamber components having such a surface include, butare not limited to, windows and view ports (collectively, “windows”).Through the processing of semiconductor substrate materials, organicmaterials (for example, finger oils, grease, particles and organiccompounds); metals (for example, aluminum, molybdenum, and tungsten);dielectric materials (for example, silicon dioxide and silicon nitride);and other inorganic materials can become deposited onto such windows.Such windows are typically cleaned in an ultrasonic bath. However,conventional baths and cleaning methods suffer from an inability toprovide particle-free, or consistently particle-free, results. This isbecause such baths and methods fail to remove all particles from thewindow or some of the particles that do get removed recirculate in thebath and redeposit on the window.

Whether cleaning plasma processing chamber components or other articles,there remains a need for better cleaning apparatuses and methods ofobtaining ultra-clean articles.

SUMMARY

The present disclosure provides, in various embodiments, a novelultrasonic cleaning apparatus and methods of obtaining an ultra-cleanarticle using said apparatus. In some of the various embodiments, theultrasonic cleaning apparatus comprises (i) a substantially circulartank; (ii) a plurality of cleaning fluid inlets for delivering acleaning fluid to the tank; (iii) an intermediate support for receivingan article to be cleaned; and (iv) an ultrasonic generator coupled tothe tank for generating ultrasonic waves in the tank and cleaning fluidreceived therein. The provided apparatus is configured to deliver andreceive cleaning fluid to the tank via the inlets, remove particles froman article supported in the tank and cleaning fluid, and direct flow ofcleaning fluid such that removed particles are carried away from thearticle and out of the tank with low incidence of recirculation(stagnation) within the tank. Thus, the apparatus is configured toremove particles and inhibit redeposition thereof onto the article.

In some of the various embodiments, the provided methods of cleaning anarticle comprise (i) providing an ultrasonic cleaning apparatusdescribed herein; (ii) introducing an article to be cleaned into thetank; (iii) introducing a cleaning fluid into the tank through theplurality of cleaning fluid inlets; and (iv) exciting the cleaning fluidwith ultrasonic waves.

Although the present disclosure is not intended to be limited to aparticular article to be cleaned or a particular application, in someembodiments the provided apparatus and methods are configured to cleanquartz articles of a plasma processing chamber. As used herein, a“quartz article” means a component having at least one quartz surface.Examples of such articles include, but are not limited to, dielectricwindows, process gas injectors, injection rings, view ports, plasmaconfinement rings, focus rings and edge rings surrounding a substrate ona substrate support, and gas distribution plates and baffles fordistributing process gases. Such articles have various shapes, and theprovided apparatus (and various components thereof) may be configured toaccommodate such shapes. Thus, in some embodiments, the providedapparatus and methods are configured to clean substantially planarquartz articles. An example of such an article is a quartz window. Insuch embodiments, the window can be placed into the tank such that aplasma-facing surface of the window is oriented to face the bottomportion of the tank and the opposing exterior-facing surface of thewindow is oriented to face the top portion of the tank.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the many embodiments of the presentdisclosure will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 illustrates one example of a provided ultrasonic cleaningapparatus and assembly thereof with a substantially planar article to becleaned;

FIG. 2 illustrates certain optional configurations of the providedapparatus, namely how cleaning fluid may (i) flow through an innercircumferential fluid gap between a substantially planar article and anintermediate support submerged in the tank; and/or (ii) flow through anouter circumferential fluid gap between the intermediate support andtank sidewall;

FIG. 3 is A, a bottom view (bottom of tank not shown) of one example ofa provided cleaning apparatus assembled with a substantially planararticle to be cleaned, said view illustrating an apparatus having fourequidistantly placed cleaning fluid inlets, each disposed within aradial cleaning fluid passage of the intermediate support; and B, oneexample of an angled nozzle injector;

FIG. 4 illustrates one example of how the apparatus of FIG. 3 can beconfigured to direct flow of cleaning fluid between the bottom of thetank and the bottom-facing surface of the article to be cleaned;

FIG. 5 is A, a bottom view (bottom of tank not shown) of one example ofa provided cleaning apparatus assembled with a substantially planararticle to be cleaned, said view illustrating an apparatus having twoequidistantly placed cleaning fluid inlets, each disposed within aradial cleaning fluid passage of the intermediate support; B, oneexample of an multi-slotted fan injector, each slot being in a differentplane; and C, an example of how the multi-slotted fan injector can beconfigured to deliver cleaning fluid into the tank; and

FIG. 6 illustrates one example of how the apparatus of FIG. 5 can beconfigured to direct flow of cleaning fluid between the bottom of thetank and the bottom-facing surface of the article to be cleaned.

DETAILED DESCRIPTION

Specific embodiments of the present disclosure will now be described.The invention may, however, be embodied in different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete and will fully convey the scope of the same to thoseskilled in the art.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. The terminology used in thepresent disclosure is for describing particular embodiments only and isnot intended to be limiting. As used in the specification and appendedclaims, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise.

It is noted that recitations herein of “at least one” component,element, etc., should not be used to create an inference that thealternative use of the articles “a” or “an” should be limited to asingle component, element, etc.

It is noted that recitations herein of a component of the presentdisclosure being “configured” to embody a particular property, orfunction in a particular manner, are structural recitations, as opposedto recitations of intended use. More specifically, the references hereinto the manner in which a component is “configured” denotes an existingphysical condition of the component and, as such, is to be taken as adefinite recitation of the structural characteristics of the component.

It is noted that terms like “preferably,” “commonly,” and “typically,”when utilized herein, are not utilized to limit the scope of the claimedinvention or to imply that certain features are critical, essential, oreven important to the structure or function of the claimed invention.Rather, these terms are merely intended to identify particular aspectsof an embodiment of the present disclosure or to emphasize alternativeor additional features that may or may not be utilized in a particularembodiment of the present disclosure.

It is further noted that the terms “substantially” and “approximately”are utilized herein to represent the inherent degree of uncertainty thatmay be attributed to any quantitative comparison, value, measurement, orother representation. The terms “substantially” and “approximately” arealso utilized herein to represent the degree by which a quantitativerepresentation may vary from a stated reference without resulting in achange in the basic function of the subject matter at issue.

Unless otherwise indicated, all numbers expressing quantities,properties, conditions, and so forth as used in the specification andclaims are to be understood as being modified in all instances by theterm “about.” Additionally, the disclosure of any ranges in thespecification and claims are to be understood as including the rangeitself and also anything subsumed therein, as well as endpoints.Notwithstanding that numerical ranges and parameters setting forth thebroad scope of the disclosure are approximations, the numerical valuesset forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from error found in their respectivemeasurements.

Apparatus

In various embodiments of the present disclosure, provided is anultrasonic cleaning apparatus configured to deliver and receive cleaningfluid from a plurality of cleaning fluid inlets, remove particles froman article to be cleaned, and direct flow of cleaning fluid such thatremoved particles are carried away from the article and out of a tank.Additionally, the apparatus is configured to carry removed particles outof the tank with low incidence of recirculation (stagnation) within thetank, thereby inhibiting redeposition onto the cleaned article. In someof the various embodiments, the provided apparatus comprises (i) asubstantially circular tank comprising a top portion, a bottom portion,and a sidewall disposed therebetween; (ii) a plurality of cleaning fluidinlets for delivering a cleaning fluid to the tank; (iii) anintermediate support for receiving an article to be cleaned, the supportconfigured to maintain the article submerged in cleaning fluid but abovethe plurality of cleaning fluid inlets; and (iv) an ultrasonic generatorcoupled to the tank for generating ultrasonic waves in the tank andcleaning fluid received therein.

The provided apparatus comprises a “substantially circular” tank. Thus,the tank may have a uniform radius, or it may have a radius thatdeviates somewhat (i.e., not a perfect circle). It is also contemplatedthat a tank having a similar shape may also be substituted withoutdeviating from the general scope of the present disclosure. For example,an oval tank is specifically contemplated. Whether circular,substantially circular, or oval, the provided tank comprises a topportion, a bottom portion, and a sidewall disposed therebetween. In someembodiments, the bottom portion and sidewall may be integrally formed.In some embodiments, the bottom portion and sidewall are separatecomponents that are mechanically joined such that a cleaning fluid canbe received by the tank without leakage. While the top portion istypically open, it also may comprise a lid. The sidewall may alsocomprise a plurality of apertures proximate to the bottom portion, suchapertures being configured to at least partially receive the cleaningfluid inlets. In some embodiments, such apertures (and associatedcleaning fluid inlets) may be equidistantly spaced around thecircumference of the tank sidewall. The sidewall additionally maycomprise a plurality of apertures proximate to the top portion, suchapertures being configured to be outlet ports for cleaning fluid andremoved particles carried by the flow thereof through the tank. Suchfluid outlet ports may be the apertures themselves or be an article(such as a nozzle, tube, injector, or connector) at least partiallydisposed therein. In some embodiments, such apertures (and associatedfluid outlet ports) may be equidistantly spaced around the circumferenceof the tank sidewall. The number of fluid outlet ports proximate to thetop portion of the tank may be the same as or different from the numberof cleaning fluid inlets proximate to the bottom portion of the tank. Asnon-limiting examples, the apparatus may be configured to have twocleaning fluid inlets and two fluid outlet ports; four cleaning fluidinlets and four fluid outlet ports; four cleaning fluid inlets and twofluid outlet ports; or six cleaning fluid inlets and two fluid outletports.

The provided apparatus also comprises an intermediate support. Thesupport can be manufactured from a variety of materials, provided thatsuch materials are suitable for the specific application. A non-limitingexample of a material of construction is polytetrafluoroethylene(Teflon®; DuPont). In addition to materials of construction, the designof the intermediate support can also be tailored to meet the needs of aspecific application. The provided intermediate support comprises anupper support surface and a base structure opposite the upper supportsurface and is configured to define a plurality of radial cleaning fluidpassages extending through the base structure from the outercircumference of the support to an inner circumference of the support.The inner circumference of the intermediate support can be modified toallow more or less of the bottom-facing surface of the article to becleaned to be directly contacted by cleaning fluid. The outercircumference of the intermediate support is, in some embodiments,approximately equal to an inner circumference of the tank sidewall.

The provided intermediate support is configured such that when disposedin the tank, the base structure contacts the bottom portion of the tankand the plurality of inlets are disposed within the plurality of radialcleaning fluid passages of the support. Thus, the article to be cleanedis maintained by the support within the cleaning fluid above thepluralityof inlets. In some embodiments, the intermediate support can beconfigured to define one or both of (i) a substantially continuous outercircumferential fluid gap between a substantial entirety of an outercircumference of the support and an inner circumference of the tank; and(ii) a substantially discontinuous inner circumferential fluid gapbetween an intermediate circumference of the support and a substantiallyplanar article supported by the upper support surface of the support. Insome embodiments, the article to be cleaned has one or more apertures,and the provided apparatus is configured to direct flow of cleaningfluid from the plurality of inlets through such apertures.

As indicated, the provided apparatus comprises a plurality of inlets fordelivering a cleaning fluid to the tank. In some embodiments, eachcleaning fluid inlet is equidistantly spaced from the other. Forexample, in such embodiments an apparatus having two inlets would havesuch inlets oriented 180° from each other around the circumference ofthe tank. Similarly, an apparatus of such embodiments having threeinlets would have such inlets oriented 120° from each other around thecircumference of the tank. As another example of such embodiments, if anapparatus has four inlets, each would be oriented 90° from theneighboring inlet. Moreover, in such an apparatus having six inlets,each would be oriented 60° from the neighboring inlet. The basestructure of the intermediate support can be configured to accommodateone, two, three, four, five, six, or more inlets, each inlet beingdisposed within a radial cleaning fluid passage of the support.

The provided apparatus is configured to direct cleaning fluid such thatremoved particles are carried away from the article and out of the tankwith low incidence of recirculation. Thus, the apparatus is configuredto provide an ultra-clean article by removing particles and inhibitingredeposition thereof onto the article. In part, selection of the numberof cleaning fluid inlets helps to achieve desired flow hydrodynamics.Selection of the type of cleaning fluid inlet is another factor forachieving such flow hydrodynamics. Suitable cleaning fluid inletsinclude, but are not limited to, nozzle injectors (also referred to ajet injectors), fan injectors, and combinations thereof. Thus, anapparatus having only nozzle injectors, an apparatus having only faninjectors, and an apparatus having nozzle and fan injectors are allcontemplated.

In some embodiments, the provided apparatus comprises cleaning fluidinlets that are nozzle injectors. Such nozzle injectors may be straight(directing flow to the center of the tank) or may be angled (directingflow to a predetermined offset). Angled nozzle injectors may be selectedwhen greater vorticle motion of cleaning fluid is desired. Accordingly,when an angled nozzle injector is used, it is typically configured todirect fluid flow in the same general direction as a neighboring anglednozzle injector. In some embodiments, the cleaning fluid inlets of theapparatus are angled nozzle injectors, each having an offset angle of20° (with respect to a line through the center of the tank). However,other offset angles are also within the scope of the present disclosure.For example, nozzle injectors having an offset angle of 0°-10°, 10°-20°,20°-30°, 30°-40°, 40°-50°, 50°-60°, 60°-70°, 70°-80°, and 80°-90° arespecifically contemplated. For clarity, an offset angle of 0° means thatflow is directed along a line through the center of the tank, and anoffset angle of 90° means that flow is directed perpendicular to a linethrough the center of the tank. In some embodiments, the providedapparatus comprises four angled nozzle injectors, each having an offsetangle of 20°.

In some embodiments, the provided apparatus comprises cleaning fluidinlets that are fan injectors. Such injectors can be configured assingle-slotted injectors or multi-slotted fan injectors, each slotconfigured to introduce fluid in a fan (or arc) of a predeterminedcoverage angle. In some emodiments, the cleaning fluid inlets of theapparatus are single-slotted injectors. For example, the apparatus maycomprise single-slotted injectors wherein the fan coverage angle is from0°-30°, 30°-60°, 60°-90°, 90°-120°, 120°-150°, and 150°-180°. Forclarity, a fan coverage angle of 0° means that there is no fan of fluid,a fan coverage angle of 60° means that fluid is injected in a fan (arc)of 60°, and a fan coverage angle of 180° means that fluid is injected ina fan (arc) of 180°. With respect to fluid injection, the cleaning fluidinlets can be configured to orient the fan in various ways. For example,with a fan coverage of 90°, the fan can be oriented such that the fancoverage is along a line through the center of the tank and throughout afan that is 90° therefrom, or the fan can be oriented such that the fanis along a line through the center of the tank and throughout 45° inopposing directions therefrom. In some embodiments, the providedapparatus comprises two or four single-slotted fan injectors, each slotconfigured to introduce fluid in a fan of 90°, 120°, or 180° coverage.

The cleaning fluid inlets of the apparatus may, in some embodiments, bemulti-slotted injectors, such injectors having two, three, four, five,six, seven, or more slots. As with the single-slotted injector, eachslot is configured to introduce fluid in a fan of a predeterminedcoverage angle. For example, the apparatus may comprise multi-slottedinjectors wherein the fan coverage angle of each slot is independentlyselected from 0°-30°, 30°-60°, 60°-90°, 90°-120°, 120°-150°, and150°-180°. A multi-slotted injector can have slots arranged in the sameor different planes. For example, a two-slotted injector can have twoadjacent slots existing in the same plane or two slots on top of eachother (i.e., in different planes). In those embodiments wherein slotsexist in the same plane, the inlet can be configured such that the fansof the slots do or do not overlap. For example, a two-slotted injectorhaving two 120° fans in the same plane can be configured to provide acumulative fan coverage angle of 180°, wherein there is 60° overlap. Asanother example, a two-slotted injector having two 90° fans in the sameplane can be configured to provide a cumulative fan coverage angle of180°, wherein there is no overlap. Moreover, coverage gaps may also beintroduced between fans. In those embodiments wherein slots exist inseparate planes, the slots can be configured to be on top of each other.For example, an injector may have seven slots on top of each other, eachslot having the same or different fan coverage angle of a neighboringslot. In some embodiments, the provided apparatus may comprise twoseven-slotted fan injectors, each slot configured to introduce fluid ina fan of 180° coverage.

As indicated, the apparatus is configured to support an article (forexample, a substantially planar article) above the plurality of cleaningfluid inlets such that the surface of the article oriented to face thebottom of the tank is directly contacted with cleaning fluid. Theapparatus is also configured such that the surface of the articleoriented to face the top of the tank is also contacted with cleaningfluid. After being injected into the tank via the cleaning fluid inlets,the cleaning fluid flows by the bottom-facing surface of the article andtowards the top of the tank. More particularly, the fluid flows towards(and out of) the plurality of fluid outlet ports proximate to the topportion of the tank and in such process also flows by the top-facingsurface of the article. Thus, in those embodiments wherein theintermediate support is configured such that there is limited flow ofcleaning fluid between the outer circumference of the support and theinner circumference of the tank sidewall, there must be some otherpathway by which the cleaning fluid can flow from (and by) thebottom-facing surface to (and by) the top-facing surface of the article.Similarly, in those embodiments wherein the support is configured suchthat there is little or no flow of cleaning fluid between the supportand the article to be cleaned, there must be some other pathway by whichthe cleaning fluid can flow from (and by) the bottom-facing surface to(and by) the top-facing surface of the article. In some embodiments, thearticle to be cleaned has one or more apertures, and the providedapparatus is configured such that the main flow of cleaning fluid isdirected from the plurality of cleaning fluid inlets, by thebottom-facing surface of the article, through the one or more aperturesof the article, by the top-facing surface of the article, and to (andout of) the plurality of fluid outlet ports proximate to the top portionof the tank. In such embodiments, the apparatus may be configured suchthat there is vortical motion of cleaning fluid below the bottom-facingsurface of the article, above the top-facing surface of the article, orboth.

The provided apparatus additionally comprises an ultrasonic generatorcoupled to the tank. While ultrasonic generators are generally familiarto those of skill in the art, a suitable one for the provided apparatusis one capable of providing suitable power density for an application.The size of the tank is one factor in selection of a suitable generator.

In certain embodiments, the provided apparatus is specificallyconfigured to receive and clean plasma processing chamber windows. Insuch embodiments, the intermediate support is configured to receive asubstantially planar window that is placed into the tank with theplasma-facing surface of the window oriented toward the bottom portionof the tank and the opposing exterior-facing surface of the windoworiented toward the top portion of the tank. However, the intermediatesupport could alternatively be configured to receive the window in theopposite orientation. A plasma processing chamber window may have one ormore apertures. For example, a single aperture disposed in the center ofa round window. For such a window, the provided apparatus is configuredsuch that the main flow of cleaning fluid is directed from the pluralityof inlets, by the plasma-facing surface of the window (when oriented toface the bottom portion of the tank), through the window aperture, bythe exterior-facing surface of the window (when oriented to face the topportion of the tank), and to (and out of) the plurality of fluid outletports proximate to the top portion of the tank. In such embodiments, atleast the plasma-facing surface of the window is contacted withultrasonic waves. Optionally, the exterior-facing surface may also becontacted with ultrasonic waves. In either instance, the apparatus isconfigured to remove particles from the window surfaces and carry themaway from the article with low incidence of recirculation (stagnation)within the tank, thereby inhibiting redeposition onto the window. Thus,the apparatus is suitable for use in providing an ultra-clean window.

Methods

In various embodiments of the present disclosure, also provided aremethods of cleaning an article. Such methods comprise (i) providing anultrasonic cleaning apparatus as described herein; (ii) introducing anarticle to be cleaned into the tank of the apparatus; (iii) introducinga cleaning fluid into the tank through the plurality of inlets of theapparatus; and (iv) exciting the cleaning fluid with ultrasonic waves.In some embodiments, the provided methods are directed to cleaning asubstantially planar article, including a plasma processing chamberwindow.

The provided cleaning apparatus comprises an intermediate support forreceiving the article to be cleaned. The provided intermediate supportcomprises an upper support surface and a base structure opposite theupper support surface and is configured to define a plurality of radialcleaning fluid passages extending through the base structure from theouter circumference of the support to an inner circumference of thesupport. In some embodiments, the support has an open interior portionthat enables cleaning fluid to directly contact at least one surface ofthe article oriented to face the bottom portion of the tank. Theintermediate support is configured such that when disposed in the tank,the base structure contacts the bottom portion of the tank and theplurality of cleaning fluid inlets are disposed within the plurality ofradial cleaning fluid passages. Thus, the article to be cleaned ismaintained by the support in the cleaning fluid above the plurality ofcleaning fluid inlets. In some embodiments of the provided methods, thearticle to be cleaned can be received by the support outside of thetank, and the support and received article can be subsequentlyintroduced into the tank. In other embodiments, the support can bedisposed within the tank and the article to be cleaned can be receivedby such support while still in the tank.

The provided cleaning apparatus comprises a plurality of cleaning fluidinlets for delivering a cleaning fluid to the tank. Suitable cleaningfluid inlets include, but are not limited to, nozzle injectors (alsoreferred to a jet injectors), fan injectors, and combinations thereof.In the provided methods, cleaning fluid is introduced into the tankthrough the plurality of cleaning fluid inlets. The tank may or may notcontain cleaning fluid prior to the introduction of the article to becleaned. In either instance, once the article has been introduced intothe tank, cleaning fluid is introduced into the tank through theplurality of cleaning fluid inlets. Cleaning fluid may be introducedinto the tank through an inlet a predetermined flow rate. For example,cleaning fluid may be introduced into the tank through cleaning fluidinlets at a flow rate of 0-1 L/minute, 1-2 L/minute, 2-3 L/minute, 3-4L/minute, or 4-5 L/minute. It is also contemplated that the flow rate ofone inlet of the apparatus may the same or different from the flow rateof another inlet of the apparatus. In some embodiments, the cleaningfluid is introduced into the tank a continous flow rate (for example,continuously at 2 L/minute). In some embodiments, the cleaning fluid isintroduced into the tank at a variable flow rate (for example, initiallyat a flow rate of 2 L/minute and subsequently at a reduced flow rate).In some embodiments, one or more pauses in flow may be introduced (forexample, an initial flow of 2 L/minute, a pause of 10 seconds, and asubsequent flow of 2 L/minute). In such embodiments, the length of thepause can be suited to the particular application and article to becleaned. As non-limiting examples, the pause can be 0-5 seconds, 5-10seconds, 10-15 seconds, or 15-20 seconds.

Once cleaning fluid is introduced into the tank, it flows from theplurality of cleaning fluid inlets, by at least the surface of thearticle oriented to face the bottom portion of the tank, to (and by) thesurface of the article oriented to face the top portion of the tank, andto (and out of) the plurality of cleaning fluid outlets proximate to thetop portion of the tank. The hydrodynamics of the cleaning fluid floware configured to carry particles removed from the article away from thearticle and out of the tank with low incidence of recirculation withinthe tank, thereby inhibiting particle redeposition. In those embodimentswherein the method comprises pausing the flow rate, such pause may beused to help disrupt recirculation of removed particles within the tank.

The cleaning fluid introduced into the tank can be any fluid suitablefor the application and suitable for use with ultrasound. In someembodiments, the cleaning fluid can be water, an organic solvent, anacidic solution, or a basic solution. For example, the cleaning fluidcan be selected from water (H₂O), methanol (CH₃OH), ethanol (C₂H₅OH),isopropyl alcohol (C₃H₇OH), acetone (C₃H₆O), ammonium hydroxide (NH₄OH),hydrogen peroxide (H₂O₂), hydrochloric acid (HCl), hydrofluoric acid(HF), nitric acid (HNO₃), acetic acid (C₂H₄O₂), or combinations thereof.In the provided methods, one cleaning fluid (or combination of cleaningfluids) can be introduced into the tank and the article contactedtherewith, followed by flushing of such cleaning fluid from the tank andsubsequent introduction of a different cleaning fluid (or combination ofcleaning fluids) into the tank. In some embodiments, it is contemplatedthat the apparatus may further comprise a heating or cooling element andthe introduced cleaning fluid may be heated or cooled as needed for aparticular application.

Once cleaning fluid has been introduced into the tank, it is excited byultrasonic waves. At least the surface of the article oriented to facethe bottom portion of the tank is contacted with ultrasonic waves.Optionally, other surfaces (including the surface oriented to face thetop portion of the tank) may also be contacted with ultrasonic waves.The ultrasonic power density used can be that suitable for a particularapplication and article. For example, power density may be 5-10 W/in²,10-15 W/in², 15-20 W/in², or 20-25 W/in². In some embodiments,ultrasonic waves may be introduced at a continous power density (forexample, continuously at 15 W/in²). In some embodiments, the ultrasonicsource of the apparatus may have an adjustable frequency or strength ofwaves to be generated and such waves are introduced at a variable powerdensity (for example, initially at 15 W/in² and subsequently at 20W/in²). In some embodiments, one or more pauses in ultrasonic wavegeneration may be introduced (for example, initially at 15 W/in², apause of 10 seconds, and subsequently at 20 W/in²). In such embodiments,the length of the pause can be suited to the particular application andarticle to be cleaned. As non-limiting examples, the pause can be 0-5seconds, 5-10 seconds, 10-15 seconds, or 15-20 seconds.

The provided methods, in certain embodiments, are configured forcleaning substantially planar articles (including, but not limited to,plasma processing chamber windows). In such embodiments, the apparatusis also configured for cleaning such articles. In methods configured forcleaning plasma processing chamber windows, the window is received bythe intermediate support such that the plasma-facing surface of thewindow is oriented toward the bottom portion of the tank and theopposing exterior-facing surface of the window is oriented toward thetop portion of the tank. However, the window could alternatively bereceived by the support in the opposite orientation. When cleaning fluidis introduced into the tank, it flows from the plurality of cleaningfluid inlets, by the plasma-facing surface of the window (when orientedto face the bottom portion of the tank), through the window aperture, bythe exterior-facing surface of the window (when oriented to face the topportion of the tank), and to (and out of) the plurality of fluid outletports proximate to the top portion of the tank. In such embodiments, atleast the plasma-facing surface of the window is contacted withultrasonic waves. Optionally, the exterior-facing surface may also becontacted with ultrasonic waves. In either instance, the apparatus isconfigured to remove particles from the window surfaces and carry themout of the tank with low incidence of recirculation (stagnation),thereby inhibiting particle redeposition. Thus, the provided methods aresuitable for providing an ultra-clean window.

EXAMPLES

The described embodiments will be better understood by reference to thefollowing examples which are offered by way of illustration and whichone of skill in the art will recognize are not meant to be limiting.

Example 1

As illustrated in FIG. 1, a provided apparatus 100 may be configured toclean substantially planar articles including, but not limited to,quartz windows 105 of a plasma processing chamber. Such apparatus 100comprises a substantially circular tank 110 comprising a top portion115, a bottom portion 120, and a sidewall 125 disposed therebetween. Thesidewall 125 has a plurality of apertures 130 proximate to the bottomportion 120 and a plurality of fluid outlet ports 135 proximate to thetop portion 115. The apparatus 100 further comprises a plurality ofcleaning fluid inlets (not shown) for delivering a cleaning fluid to thetank 110, each inlet at least partially disposed within one of theapertures 130 proximate to the bottom portion 120 of the tank 110.

The apparatus 100 additionally comprises an intermediate support 140configured to maintain a window 105 suspended in the tank 110 andcleaning fluid above the plurality of cleaning fluid inlets and belowthe plurality of fluid outlet ports 135 proximate to the top portion 115of the tank 110. The intermediate support 140 comprises an upper supportsurface 145 and a base structure 150. The base structure 150 comprises aplurality of radial cleaning fluid passages 155 extending through thebase structure 150 from the outer circumference (not labeled) of thesupport 140 to an inner circumference (not labeled) of the support 140.

The apparatus 100 is configured to receive cleaning fluid from thecleaning fluid inlets, remove particles from a quartz window 105, anddirect flow of cleaning fluid at least up through the aperture 165 ofthe quartz window 105 such that removed particles are carried away fromthe quartz window 105 and out of the tank. As illustrated in FIG. 2, theintermediate support 215 may be configured to receive the window 200 ina manner such that the plasma-facing surface 205 of the window 200 isoriented to face the bottom portion (not labeled) of the tank. In suchembodiments, cleaning fluid can additionally flow across theplasma-facing surface 205 of the window 200 and (i) up through anaperture (not shown) in the window 200; (ii) up through a substantiallydiscontinuous inner circumferential fluid gap 210 between the window 200and an intermediate circumference (not labeled) of the support 215;(iii) up through a substantially continuous outer circumferential fluidgap 220 between an outer circumference (not labeled) of the support 215and an inner circumference of the tank sidewall 225; or (iv)combinations thereof. Before exiting the tank, the cleaning fluid flowsacross at least a portion of the other surface 230 of the quartz window200.

Example 2

As illustrated in FIG. 3, the provided apparatus 300 comprises anintermediate support 305. The bottom of the support 305 is shown. Thebase structure 310 of the support 305 comprises a plurality of radialcleaning fluid passages 315 extending through the base structure 310from an outer circumference to an inner circumference. The apparatus 300further comprises a plurality of cleaning fluid inlets 325 fordelivering cleaning fluid to the tank 320. Among the types of inlets 325that can be selected are angled nozzle injectors. As shown, theapparatus 300 has four equidistantly spaced injectors 325, each havingan offset angle of approximately 20°. However, other offset angles arealso within the scope of the present disclosure. In the configurationshown, cleaning fluid flow can be directed across the bottom-facingwindow surface 330 (for example, the plasma-facing surface of thewindow). FIG. 4 illustrates that when the offset angle of each injector400 is oriented in the same general direction, vortical flow of thecleaning fluid is introduced in the tank 405 and across thebottom-facing (plasma-facing) surface 410 of the quartz window 415.

Example 3

As illustrated in FIG. 5, the provided apparatus 500 comprises aplurality of cleaning fluid inlets 510 for delivering cleaning fluidinto the tank 505. Among the types of inlets 510 that can be selectedare fan injectors. As shown, the apparatus 500 has two seven-slotted faninjectors 510, each slot 515 configured to introduce fluid in a fan ofapproximately 180° coverage. However, other fan coverage angles are alsocontemplated. As illustrated in FIG. 6, with such injectors 600 in suchconfiguration, vortical flow of the cleaning fluid is introduced in thetank 605 and across the bottom-facing (plasma-facing) surface 610 of thequartz window 615 with low incidence of recirculation.

The present disclosure should not be considered limited to the specificexamples described herein. Various modifications, equivalent processes,as well as numerous structures and devices to which the presentdisclosure may be applicable will be readily apparent to those of skillin the art. Those skilled in the art will understand that variouschanges may be made without departing from the scope of the disclosure,which is not to be considered limited to what is described in thespecification.

What is claimed is:
 1. An apparatus, comprising: a tank comprising a topportion, a bottom portion, and a sidewall disposed therebetween, thetank configured to contain a cleaning fluid and to receive asubstantially planar article submerged in the cleaning fluid; aplurality of cleaning fluid inlets for delivering the cleaning fluid tothe tank, each cleaning fluid inlet at least partially disposed in thesidewall; an intermediate support for receiving the substantially planararticle, the intermediate support configured to maintain thesubstantially planar article in the tank above the plurality of cleaningfluid inlets and below a plurality of fluid outlet ports disposed in thesidewall; an ultrasonic generator coupled to the tank for generatingultrasonic waves in the tank and cleaning fluid received therein;wherein the intermediate support comprises an upper support surface anda base structure opposite the upper support surface and a plurality ofradial cleaning fluid passages extending through the base structure ofthe intermediate support from an outer circumference of the intermediatesupport to an inner circumference of the intermediate support; andwherein the apparatus is configured to receive the cleaning fluid fromthe cleaning fluid inlets, remove particles from the substantiallyplanar article, and direct flow of cleaning fluid such that removedparticles are carried away from the substantially planar article and outof the tank through the fluid outlet ports.
 2. An apparatus according toclaim 1, wherein the intermediate support is configured such that whendisposed in the tank, the base structure of the support contacts thebottom portion of the tank such that the plurality of cleaning fluidinlets are disposed within the plurality of radial cleaning fluidpassages.
 3. An apparatus according to claim 1, wherein the cleaningfluid inlets are selected from nozzle injectors, fan injectors, andcombinations thereof.
 4. An apparatus according to claim 3, wherein thecleaning fluid inlets are angled nozzle injectors.
 5. An apparatusaccording to claim 4 comprising four angled nozzle injectors, eachhaving an offset angle of 20°.
 6. An apparatus according to claim 5,wherein the four angled nozzle injectors are equidistantly spaced aroundthe circumference of the tank.
 7. An apparatus according to claim 3,wherein the cleaning fluid inlets are multi-slotted fan injectors.
 8. Anapparatus according to claim 7 comprising two seven-slotted faninjectors, each slot configured to introduce cleaning fluid in a 180°fan.
 9. An apparatus according to claim 8, wherein the two seven-slottedfan injectors are equidistantly spaced around the circumference of thetank.
 10. An apparatus according to claim 1, wherein the apparatus isconfigured to receive and clean a plasma processing chamber window. 11.An apparatus according to claim 10, wherein the apparatus is configuredto receive the window such that a plasma-facing surface of the window isoriented to face the bottom portion of the tank.
 12. An apparatusaccording to claim 1, wherein the intermediate support is furtherconfigured to provide a substantially continuous outer circumferentialfluid gap between a substantial entirety of an outer circumference ofthe intermediate support and an inner circumference of the tank and asubstantially discontinuous inner circumferential fluid gap between anintermediate circumference of the intermediate support and thesubstantially planar article supported by the upper support surface ofthe intermediate support.
 13. A method of cleaning a substantiallyplanar article, comprising: providing a tank comprising (i) a topportion, (ii) a bottom portion, and (iii) a sidewall disposedtherebetween, the tank configured to contain a cleaning fluid and toreceive a substantially planar article submerged in the cleaning fluid;(iv) a plurality of cleaning fluid inlets at least partially disposed inthe sidewall; (v) a plurality of fluid outlet ports disposed in thesidewall; (vi) an intermediate support for receiving the substantiallyplanar article, the support comprising an upper support surface, a basestructure opposite the upper support surface, and a plurality of radialcleaning fluid passages extending through the base structure from anouter circumference of the support to an inner circumference of thesupport; and (vii) an ultrasonic generator coupled to the tank forgenerating ultrasonic waves in the tank and the cleaning fluid receivedtherein; introducing the substantially planar article to be cleaned intothe tank such that the substantially planar article is received andmaintained by the support above the plurality of cleaning fluid inletsand below the plurality of fluid outlet ports; introducing the cleaningfluid into the tank through the plurality of cleaning fluid inlets;exciting the cleaning fluid with ultrasonic waves; and allowing thecleaning fluid to flow out of the tank through the plurality of fluidoutlet ports; wherein particles are removed from the substantiallyplanar article and carried by flow of the cleaning fluid away from thesubstantially planar article and out of the tank.
 14. A method accordingto claim 13, wherein the substantially planar article is a plasmaprocessing chamber window having a plasma-facing surface and an opposingexterior-facing surface, and wherein the window is introduced into thetank such that the plasma-facing surface is oriented toward the bottomportion of the tank.
 15. A method according to claim 14, wherein thecleaning fluid inlets of the apparatus are selected from nozzleinjectors, fan injectors, and combinations thereof.
 16. A methodaccording to claim 15, wherein cleaning fluid is introduced into thetank through either (i) four angled nozzle injectors, each having anoffset angle of 20°; or (ii) two seven-slotted fan injectors, each slotconfigured to introduce cleaning fluid in a 180° fan.